The present invention relates to a battery charger and, in particular, to a battery charger that automatically provides the correct polarity current to the battery independent of the terminal connections.
Users of battery chargers often connect the battery charger to the battery to be charged with the wrong polarity terminals connected. This can damage the charger, the battery or both. Various devices have been proposed to prevent this problem. U.S. Pat. Nos. 3,781,631 and 3,857,082 show battery chargers that detect reverse polarity and disable the charger's current output in response.
While protecting the battery and charger, this method requires the user to recognize the problem and to reverse the connections.
U.S. Pat. No. 4,876,496 shows a battery charger that automatically steers the charging current to the correct polarity terminals. A separate full-wave center-tapped rectifier supplies the charging current to an SCR switching network controlled by a battery polarity sensing circuit. The SCR network only routes the current, which has already been converted from a.c. to d.c.